I agree with Wolfgang. Check that the optical path lengths for the two
arms are nearly equal. When we got our Ealing(!!) interferometers they
were so far off that you could not get a white light pattern, and could
hardly get any pattern at all even with a laser. We had to put in a shim
over 7 mm thick in one arm.

Dick Berg

On Fri, 2 Feb 2001, Wolfgang Rueckner wrote:

> One thing that no one has mentioned -- do you have the compensating piece
> of glass in there? If not, no amount of alignment will get you anywhere.
> Wolfgang
>
>
>
> >Hi everyone,
> >
> >I am having an incredibly difficult time getting our Michelson
> >interferometer working, much to the chagrin of a certain difficult faculty
> >member (but that's another story altogether).
> >
> >I am using a standard HeNe laser (1mW, I believe), expanded by a factor of
> >ten by two lenses I purchased from Pasco (not the most expensive lenses,
> >but the resulting beam seems pretty clean), incident upon our
> >interferometer. I have no problem getting the two beams to overlap, and I
> >am seeing some kind of fringes, but they don't move when I crank the
> >micrometer. I suspect that these fringes result from reflections from the
> >front and back faces of the silvered mirror, based upon the fact that each
> >beam exhibits fringes, even when the other beam is blocked.
> >
> >Can anyone offer me some wisdom to solve this problem before it costs me my
> >job? (OK, I'm exaggerating slightly...but it's really important that I get
> >this working)
> >
> >Scott
>
>
>